This invention relates to chain saw blades and particularly to means for providing a visual guide for the proper positioning of a filing device for optimum sharpening of the chain saw tooth. The invention further relates to means for providing a visual guide for the proper positioning and shape of the hook which forms part of the chain saw tooth.
A chain saw blade may be of any conventional type having an elongated chain bar mounted on and protruding from a saw body. The periphery of the bar carries an endless saw chain in a peripheral groove. Several saw teeth are mounted at spaced locations around the chain. As the chain is driven around the blade, the teeth cut into and remove wood lying adjacent to the path of the moving chain. The teeth are mounted at spaced locations on alternating sides of the saw chain and extend outwardly away from the chain bar. A saw tooth consists of a leading depth post and a trailing cutting edge. The cutting edge consists of a first segment extending outwardly and parallel to the chain bar and an integrally formed second segment which extends perpendicular to the outermost edge of the first segment across the width of the chain.
The shape of the cutting edge of the tooth forms a precisely curved "hook". The curvature of the hook is fixed during manufacture to ensure most effective cutting. During normal use, the cutting edge deteriorates and it is necessary to resharpen it. Resharpening is accomplished by applying a circular file at the exact angle set by the manufacturer in order to reform the hook to its most effective cutting shape. Maintaining this angle during filing is assisted by the use of a mechanical or visual guide. Use of mechanical or visual guides in the past has required the use of mechanical clamps or other locking devices necessary for positioning the guide next to the saw blade during the filing process. In order to accomplish rapid on-site resharpening of the chain saw tooth, it is necessary for the chain saw operator to carry these clamps or locking devices to each location that the saw is used.
It is the object of this invention to provide an improved, lightweight visual guide that can quickly and easily be attached to the blade without the need for cumbersome vises or clamps. Another object of the invention is to provide, as part of such visual guide, the capability to gauge the proper shape and location of the hook on the tooth being filed.